RE: Piston rings keeps breaking
I-fly,
First, trial-fit the ring alone in the sleeve, to verify it can go in.
There is absolutely no need for a ring compressor to do that - just manipulate it gently with your fingers and once it is in the sleeve, push it down using the piston, until it is where it will be at the top of the stroke, about 1.5 cm below the sleeve flange.
Now, make sure there is a small gap between the two ends of the ring. For full size engines, the size of the gap is .15 mm, or .006" for this piston diameter (use a feeler gage to measure).
For a two-stroke model engine it can be slightly larger.
If there is no gap the ring will not fit. If there is too large a gap, compression leakage will result; less power and harder starting.
The ring is pinned.
Search the groove in the piston to find the locating pin. This pin must be in the ring gap, so the ring will be allowed to 'sink' all the way into its groove (without protruding from it).
The purpose of this pin is to ascertain the ring ends are never caught in the intake and the exhaust port. The ring must not rotate.
When assembled, the ring gap must coincide with a clean, straight part of the sleeve, where it can never 'find' a port, while going up and down...
When fitting the sleeve into the crankcase, it must be aligned with its final position, so you would not need to rotate it as it is slid down.
The chamfer in the bottom of the sleeve serves as a makeshift 'ring compressor', as it is slid down over the piston (which is already fitted onto the con-rod and crank-pin).
The whole assembly goes in, of course, from the bottom of the sleeve...